EP0806243A1 - Method for reactivation of a platinum group metal catalytic system - Google Patents

Abstract

Reactivation of deactivated catalysts (I) containing a platinum metal and a metal co-catalyst, for oxidative carbonylation of aromatic hydroxyl compounds, comprises: (a) treating (I) at 100-400 degrees C in a liquid phase containing 1-10000 equivalents of oxidant/equivalent of metal constituents of the catalyst system; (b) separation of excess oxidant; and (c) treating the oxidised residue with 0.1-100 pts.wt. of a 1-12C carboxylate or a 4-12C diketonate per pt .wt. oxidised residue.

Description

The present invention relates to a process for reactivating platinum metal-containing catalyst systems which consist of at least one platinum metal, a cocatalyst and other salts which are used for the preparation of diaryl carbonates by oxidative reaction of aromatic hydroxy compounds with carbon monoxide, which is characterized in that the deactivated Treated catalyst system with an oxidizing agent, which separates excess oxidizing agent and mixed with the reactivated catalyst system with a diketonate.

It is known to produce diaryl carbonates by oxidative reaction of aromatic hydroxy compounds with carbon monoxide in the presence of a noble metal catalyst (DE-OS 28 15 512). Palladium is preferably used as the noble metal. In addition, a cocatalyst (e.g. manganese or cobalt salts), a base, a quaternary salt, various quinones or hydroquinones and drying agents can be used. This can be done in a solvent, preferably methylene chloride.

With continuous process control, a decrease in the space-time yield can be observed in processes of this type, which is due to a deactivation of the homogeneous catalyst system. Deactivated catalyst components precipitate out of the reaction system as powder. These powders show very little or no catalytic activity. The literature contains no information on the reactivation of this catalyst system. In order to obtain a high space-time yield, deactivated catalyst components have to be removed from the process and replaced by fresh catalyst. Because the noble metal catalyst represents a considerable cost factor and losses of noble metal catalyst have to be replaced correspondingly costly, the economy of a diaryl carbonate production process with a homogeneous catalyst system depends heavily on the consumption of platinum metal / cocatalyst. By reactivating deactivated catalyst systems, the fresh catalyst requirement of the process could be drastically reduced, so that an economical implementation is possible. The object was therefore to find a simple process with which deactivated catalyst systems can be reactivated.

It has now been found that deactivated, platinum metal-containing catalyst systems consisting of at least one platinum metal, a cocatalyst and further salts which are used for the preparation of diaryl carbonates by oxidative reaction of aromatic hydroxy compounds with carbon monoxide by treatment with an oxidizing agent and subsequent addition of a diketonate can be reactivated. The unused, excess oxidant can be recovered and used again.

The invention accordingly relates to a process for reactivating deactivated catalysts for the oxidative carbonylation of aromatic hydroxy compounds which contain a platinum metal and a cocatalytically active metal, which is characterized in that the deactivated catalysts at 10-400 ° C in the liquid phase with 1- Treated 10,000 equivalents of oxidizing agents per equivalent of the metallic components of the catalyst system, excess oxidizing agent separated and the remaining oxidized residue with 0.1-100 parts by weight of a C ₁ -C ₁₂ carboxylate or a C ₄ -C ₁₂ diketonate , based on 1 part by weight of the oxidized residue.

It is assumed that carboxylates or diketonates soluble in phenol are formed.

Metals with a catalytic action and their compounds are those of the platinum metal group, such as Ru, Rh, Pd, Ir or Pt, preferably Pd.

Co-catalytically active metals and their compounds are those of groups III B, IV B, V B, VI B, VII B, VIII B, I B, II B (CAS nomenclature) or a mixture of several of them e.g. Manganese, copper, cobalt, vanadium, preferably Mn.

The deactivated catalyst constituents are treated according to the invention with an oxidizing agent at 10 to 350 ° C., preferably at 20 to 250 ° C., particularly preferably at 30 to 200 ° C.

The oxidizing agents which can be used in the process according to the invention are those compounds or elements which, under the reaction conditions, take up electrons from the deactivated catalyst constituents; so For example, the proton H ^{+ takes up} an electron in the case of acids $${\text{2H}}^{\text{+}}{\text{+ 2 e}}^{\text{⊖}}{\text{→ H}}_{\text{2nd}}\text{.}$$

Examples of such oxidizing agents are those from the group of strong mineral acids, the elemental halogens are O ₂ , O ₃ , peroxy and hydroperoxy compounds, nitrates, permanganates, halogenates, perholognates.

The ratio of oxidizing agent to catalyst residue in the process according to the invention for liquid oxidizing agents is 10,000: 1, preferably 1000: 1, particularly preferably 500: 1. Gaseous oxidizing agents are metered in at a rate of 0.01 to 5000, preferably 0.1 to 500, particularly preferably 1 to 100 normal liters per gram of catalyst residue and hour.

For this step of the method according to the invention, a time of 0.5 to 20 h, preferably 0.5 to 10 h, particularly preferably 1 to 8 h is required.

Solid oxidizing agents (e.g. iodine, KMnO ₄ , KClO ₄ etc.) are dissolved in one of the solvents mentioned below.

Liquid oxidizing agents (eg bromine, H ₂ SO ₄ etc.) can be used neat or diluted with a polar solvent (see below).

Gaseous oxidizing agents (for example Cl ₂ , O ₂ , O ₃ , hydrogen halides, etc.) are used as a solution in one of the solvents mentioned below or are bubbled through a suspension of the deactivated catalyst in one of the solvents mentioned below.

In one possible embodiment of the process according to the invention, the catalyst residue for treatment with gaseous oxidizing agent (for example air or chlorine) is slurried in one of the solvents described above and the gaseous oxidizing agent is passed through the solution. This can take place at a pressure of 0.8 to 100 bar, preferably 0.9 to 50 bar, particularly preferably 0.9 to 10 bar. After the reaction, the solvent is preferably distilled in a known manner, the temperature and pressure being able to be varied within wide limits without the catalyst being damaged.

If liquid oxidizing agents are used, the treatment of the catalyst residue with oxidizing agent under an inert gas atmosphere (nitrogen, argon, or the like), in the air or under the atmosphere customary for the oxidative carbonylation of organic hydroxy compounds (carbon monoxide / air, carbon monoxide / oxygen) can be depressurized or be carried out under pressure. Excess oxidizing agent can, for example, be removed by distillation, even under reduced pressure or by destruction with a reducing agent.

Oxidizing agents from the group of strong mineral acids are preferred, particularly preferably from the group of H ₂ SO ₄ , HNO ₃ and hydrogen halides, very particularly preferably from the group of hydrogen halides. In particular, the hydrogen halides are used as aqueous hydrohalic acids with a concentration of 5 to 70% by weight, preferably 10 to 60% by weight, particularly preferably 15 to 50% by weight, of hydrogen halide in the total weight of the acid, preferably as aqueous hydrobromic acid.

Polar solvents are used to form the liquid phase.

Suitable polar solvents are those which do not react with the oxidizing agent provided. Examples of such solvents are those from the group of water, C ₁ -C ₄ carboxylic acids, C ₁ -C ₄ carboxylic acid esters with a C ₁ -C ₄ ester group, C ₁ -C ₄ carboxylic acid amides with an -NH ₂ - , -NH (C ₁ -C ₄ alkyl) - or -N (C ₁ -C ₄ alkyl) ₂ group, aliphatic C ₁ -C ₆ mono-, di- or polyols, (cyclo) aliphatic C ₁ -C ₆ mono- or diketones and (cyclo) aliphatic or aromatic C ₂ -C ₇ nitriles, which are used in an amount of 1 to 1,000 parts by weight, based on 1 part by weight of deactivated catalyst powder, preferably 2 to 500, particularly preferably 5 to 250 parts by weight are used. A water-containing mixture with an H ₂ O content of 10-99% of the total weight of the mixture, for example with acetic acid or propionic acid or water, preferably water, is preferably used as the polar solvent.

In the last step of the process according to the invention, the remaining, oxidized residue from the removal of the excess oxidizing agent and the polar solvent is reacted with a carboxylate of C ₁ -C ₁₂ carboxylic acids or a C ₄ -C ₁₂ diketonate, preferably with an acetate or acetylacetonate . Suitable carboxylates are, for example, formates, acetates, propionates, butyrates, pentanoates, hexanoates or capronates, with cations from the group of Li, Na, K, Mg, Ca, Mn, Fe, Co, Ce and platinum group metal contained in the catalyst to be reactivated, such as sodium formate, NaOAc, (with OAc = acetate) KOAc, sodium propionate, sodium butyrate, sodium pentanoate, sodium hexanoate or Sodium capronate, alkaline earth metal carboxylates such as Mg (OAc) ₂ or Ca (OAc) ₂ or transition metal carboxylates such as Mn (OAc) ₃ , Mn (OAc) ₂ , Fe (OAc) ₂ , Co (OAc) ₂ , Ce (OAc) ₃ or Pd ( OAc) ₂ . Suitable diketonates are those with the cations mentioned and are, for example, alkali metal acetylacetonates such as Li (acac) with acac = acetylacetonate, Na (acac), K (acac), Rb (acac) and Cs (acac), alkaline earth metal acetylacetonates such as Mg (acac) ₂ or Ca (acac) ₂ or transition metal acetylacetonates such as Cr (acac) ₃ , Mn (acac) ₂ , Mn (acac) ₃ , Fe (acac) ₂ , Fe (acac) ₃ , Co (acac) ₂ , Co (acac) ₃ Ce (acac) ₃ or Pd (acac) ₂ .

The amount of carboxylate or diketonate added in the process according to the invention is 0.1 to 100, preferably 0.2 to 50, particularly preferably 0.5 to 25 parts by weight per part by weight of oxidized catalyst residue after removal of the oxidizing agent.

The catalyst reactivated by the process according to the invention has an activity which is greater than 95% of the fresh catalyst.

The following examples illustrate the process according to the invention, but without restricting it to them.

Example 1: Reactivation:

2 g of a deactivated catalyst powder (content according to atomic absorption spectrometry: 33.9% palladium, 14.5% manganese, remainder 100%: Na ⁺ and Br ^- ions), which from a previous semibatch approach for the preparation of diphenyl carbonate (DPC; 10 bar reaction pressure, 65 ppm, Pd, about 500 ppm Mn), were added with 50 ml of a 48 wt .-% aqueous hydrogen bromide solution and heated to 100 ° C. After one hour there was a homogeneous solution. The HBr solution was then distilled off on a Rotavapor at a pressure of 30 mbar and a temperature of 80 ° C. The HBr recovery rate was 98%. The residue was air dried and weighed 3.22 g (weight gain due to Br uptake). The HBr recovered using a rotary evaporator could be reused directly.

Reuse in catalysis:

0.65 g of the reactivated catalyst (= 136 mg palladium and 58 mg manganese) and 8.31 g tetrabutylammonium bromide were dissolved in 450 g phenol at 80 ° C. in an autoclave (1 l) with a gas stirrer, cooler and downstream cold trap. Then 0.51 g of manganese (II) acetylacetonate and 2.21 g of sodium phenolate, dissolved in 50 g of phenol, were added and the pressure was brought to 10 while introducing a gas mixture of carbon monoxide and oxygen (96.5: 3.5% by volume) set in bar. The manganese content in the reaction solution was 330 ppm. The amount of gas mixture was adjusted to 260 Nl / h. A sample was taken from the reaction mixture every hour and analyzed by gas chromatography.

The analyzes showed that 7.4% diphenyl carbonate was contained in the reaction mixture after one hour, 12.2% diphenyl carbonate after 2 hours and 17.4% diphenyl carbonate after 3 hours; this corresponds to an average activity of 98.0% of the fresh catalyst used for the first time.

Comparative test with fresh catalyst:

0.34 g of palladium bromide (= 136 mg of palladium) and 8.31 g Tetrabutylammonium bromide dissolved in 450 g phenol at 80 ° C. Carbon monoxide (3 l / h) was passed through this solution for one hour to activate the catalyst. Then 0.77 g of manganese (II) acetylacetonate and 2.21 g of sodium phenolate, dissolved in 50 g of phenol, were added and the pressure was raised to 10 while introducing a gas mixture of carbon monoxide and oxygen (96.5: 3.5% by volume) set in bar. The manganese content in the reaction solution was 330 ppm. The amount of gas mixture was adjusted to 260 Nl / h. A sample was taken from the reaction mixture every hour and analyzed by gas chromatography.

The analyzes showed that after one hour 7.6% diphenyl carbonate, after 2 hours 12.4% diphenyl carbonate and after 3 hours 17.7% diphenyl carbonate were contained in the reaction mixture.

Example 2:

The procedure was as in Example 1, but the deactivated catalyst powder was not treated with 48% by weight aqueous hydrogen bromide solution, but with 98% sulfuric acid. After one hour at 100 ° C, a homogeneous solution was present. 95% of the sulfuric acid was recovered by vacuum distillation. The resulting reactivated catalyst showed an activity of 96% of the fresh catalyst when used again in the process of oxidative carbonylation of aromatic hydroxy compounds.

Example 3:

The procedure was as in Example 1, but the deactivated catalyst powder was not treated with 48% by weight aqueous hydrogen bromide solution, but with 65% nitric acid. After one hour at 80 ° C a homogeneous solution was available. 99% of the nitric acid was recovered by vacuum distillation. The resulting reactivated catalyst showed an activity of 98% of the fresh catalyst when used again in the process of oxidative carbonylation of aromatic hydroxy compounds.

Example 4:

The procedure was as in Example 1, but the deactivated catalyst powder was not with 48% by weight aqueous hydrogen bromide solution, but with 24% by weight aqueous hydrogen bromide solution treated. After one hour at 100 ° C, a homogeneous solution was present. The hydrobromic acid was 98% recovered by vacuum distillation. The resulting reactivated catalyst showed an activity of 98% of the fresh catalyst when used again in the process of oxidative carbonylation of aromatic hydroxy compounds.

Example 5:

The procedure was as in Example 1, but 1.9 g (= 15.5 mmol) of sodium acetylacetonate were added to the resulting reactivated catalyst after recovery of the hydrobromic acid.

Reuse in catalysis:

1.03 g of the reactivated catalyst (= 136 mg palladium and 58 mg manganese) and 8.31 g tetrabutylammonium bromide at 80 ° C. were dissolved in 450 g phenol in an autoclave (1 l) with a gassing stirrer, cooler and downstream cold trap. Then 0.51 g of manganese (II) acetylacetonate and 2.21 g of sodium phenolate, dissolved in 50 g of phenol, were added and the pressure was brought to 10 while introducing a gas mixture of carbon monoxide and oxygen (96.5: 3.5% by volume) set in bar. The manganese content in the reaction solution was 330 ppm. The amount of gas mixture was adjusted to 260 Nl / h. A sample was taken from the reaction mixture every hour and analyzed by gas chromatography.

The analyzes showed that after one hour 7.5% diphenyl carbonate, after 2 hours 12.3% diphenyl carbonate and after 3 hours 17.5% diphenyl carbonate were contained in the reaction mixture; this corresponds to an average activity of 98.9% of the fresh catalyst.

Claims (10)

Process for the reactivation of deactivated catalysts for the oxidative carbonylation of aromatic hydroxy compounds which contain a platinum metal and a cocatalytically active metal, characterized in that the deactivated catalysts at 10-400 ° C in the liquid phase with 1-10,000 equivalents of oxidizing agents per equivalent the metallic components of the catalyst system are treated, excess oxidizing agent is separated off and the remaining oxidized residue is treated with 0.1-100 parts by weight of a C ₁ -C ₁₂ carboxylate or a C ₄ -C ₁₂ diketonate, based on 1 part by weight. Part of the oxidized residue was added. A method according to claim 1, characterized in that the platinum metal is palladium. A method according to claim 1, characterized in that a cocatalytically active metal in bound form from the group III B, IV B, VB, VI B, VII B, VIII B, IB, II B or a mixture of several of them, preferably Mn, is present. A method according to claim 1, characterized in that an oxidizing agent from the group of strong mineral acids, the elemental halogens, O ₂ , O ₃ , peroxy and hydroperoxy compounds, nitrates, permanganates, halogenates, perhalogenates, preferably from the group of strong mineral acids, particularly preferably from the group of H ₂ SO ₄ , HNO ₃ and hydrogen halides, very particularly preferably from the group of hydrogen halides, in an amount of 1-10,000 equivalents of oxidizing agents per equivalent of the metallic constituents of the catalyst to be reactivated. A method according to claim 4, characterized in that the hydrogen halides as aqueous hydrohalic acids with a concentration of 5-70 wt .-%, preferably 10-60 wt .-%, particularly preferably 15-50 wt .-% hydrogen halide in the total weight of the acid, are preferably used as aqueous hydrobromic acid. Process according to Claim 1, characterized in that the polar solvent is one or more from the group of water, C ₁ -C ₄ carboxylic acids, C ₁ -C ₄ carboxylic esters with a C ₁ -C ₄ ester group, C ₁ -C ₄ carboxamides with a -NH ₂ -, -NH (C ₁ -C ₄ alkyl) - or -N (C ₁ -C ₄ alkyl) ₂ group, aliphatic C ₁ -C ₆ mono-, di- or polyols, (cyclo) aliphatic C ₁ -C ₆ mono- or diketones and (cyclo) aliphatic or aromatic C ₂ -C ₇ nitriles in an amount of 1 to 1,000 parts by weight, preferably 2-500, particularly preferably 5- 250 parts by weight, based on 1 part by weight of deactivated catalyst, is used. A method according to claim 6, characterized in that a water-containing mixture with an H ₂ O content of 10-99% of the total weight of the mixture or water, preferably water, is used as the polar solvent. A method according to claim 1, characterized in that as carboxylates and diketonates salts with cations from the group of alkali metals, alkaline earth metals, transition metals and the platinum group metal, which contain in the catalyst to be reactivated, preferably from the group of Li, Na, K, Mg, Ca, Mn, Fe, Co, Ce and the platinum group metal contained in the catalyst to be reactivated can be used. Process according to Claim 1, characterized in that 1 to 1,000, preferably 1 to 500 equivalents of oxidizing agent are used per equivalent of the metallic constituents of the catalyst to be reactivated. Process according to Claim 1, characterized in that 0.2 to 50, preferably 0.5 to 25 parts by weight of carboxylate or diketonate, based on 1 part by weight of the oxidized residue, are used.